Mohamed's family leaves Manhattan Federal Court after filing the lawsuit agaisnt the city of New York September, 2013 Inset: Mohamed Brah Photo: Warzer Jaff

The cops who shot and killed an emotionally disturbed African immigrant at his Harlem home last year won’t face criminal charges as a Manhattan grand jury has found they were justified in using deadly force.

The grand jury, which reached its decision Tuesday, had been secretly empanelled the past month to review the September 2012 shooting of the late Mohamed Bah.

The Guinean immigrant was killed after his mother—who was visiting from overseas for his 28th birthday – called 911 to get him medical help because he was battling severe depression. She says she expected ambulatory help – not cops to agitate her son.

“After receiving 50 exhibits and hearing testimony from 25 witnesses, including the police officers involved in incident, members of Mr. Bah’s family, neighbors and friends, the grand jury has concluded its investigation,” Manhattan DA Cyrus Vance wrote NYPD Commissioner Ray Kelly on Wednesday.

“On November 26, 2013, the grand jury was properly charged regarding the defense of justification, and voted not to bring criminal charges against any police officer involved in the shooting, finding that their use of deadly physical force was not unlawful.”

The NYPD has repeatedly defended the shooting, saying Bah was only shot because he charged at the cops naked with a butcher knife and used it to slash two cops’ bulletproof vests.

In total, 10 rounds were fired from three guns, according to Vance’s letter. Eight of the shots – six to the arm and one each to the chest and head – hit Bah.

The cops had earlier tried to hold off Bah by using a Taser weapon and firing rubber pellets, but to no avail, the letter says.

The NYPD has refused to reveal the names of the cops involved in the shooting but is still proceeding with its own internal investigation to determine whether disciplinary action is necessary.

Bah’s family in September sued the city, seekingan injunction that would require the NYPD to implement new protocols for dealing with the mentally ill.

Their lawyer, civil-rights attorney Randolph McLaughlin, was fuming Wednesday over the jury’s decision and sent a letter to Attorney General Eric Holder seeking a federal investigation into Bah’s death.

He also claims something is fishy because a key piece of evidence – “the alleged knife” cops say Bah was holding – went missing.

“[The NYPD says] it was swept away by Hurricane Sandy and mysteriously disappeared into the ocean,” McLaughlin said.

“At best, this was criminally negligent homicide. At worst, this was murder.”